Ishihara and other colour vision tests
Numbers, squiggles and the rest...
Numbers, squiggles and the rest...
Pseudoisochromatic plates (known as PICs or PIPs) were first devised by Professor J. Stilling of Strassburg in 1876 and appeared in 1883. They are a very quick hand-held test for various forms of colour-blindness and rely on the identification or non-identification of numbers or shapes against a potentially confusing coloured background. The example illustrated is from his publication Die Prüfung des Farbensinnes beim Eisenbahn und Marinepersonal (The examination of colour perception in railway and naval personnel), Cassell (1878). As Stilling pointed out in 1889 the practitioner shouldn't just rely on the patient reading out the numbers but also ask him to pick out like-coloured dots under varying conditions of distance or illumination.
The first pseudoisochromatic tests from Japan were those designed by Oguchi Chuta in 1911, but he used them to test soldiers in the Imperial Japanese Army and never published them for wider use. Our museum does not therefore possess any copies of these. The most famous Japanese pseudoisochromatic tests were designed by Ishihara Shinobu (1879-1963) Professor of Ophthalmology at the Imperial University of Tokyo between 1922-1941. Ishihara produced three manuscript versions, handpainted by himself in watercolour in the Japanese characters of katakana and hiragana and a third version in Arabic numerals. This third version developed into the International edition, first published in 1917 by the Kanahara Trading Company. Copies quickly came into widespread use in the West.
There have been numerous subsequent editions of these tests, some separate, others bound together like a book. The 1969 edition supplied in Great Britain by H.K.Lewis & Co was a bound volume of 38 coloured plates featuring both numerical and winding line tests for protanopia, protanomalia, deuteranopia, deuteranomalia, tritanomalia and total colour blindness with associated photophobia and nystagmus.
Ishihara charts are divided into five groups:
Group 1 - should be legible to all
Group 2 - should be read differently by 'normal' and 'anomalous' (colour blind) persons. For example an anomalous person will misread the number 8 for a 3
Group 3 - should be legible only to people with normal vision
Group 4 - should be legible only to people with impaired colour vision
Group 5 - will differentiate protanopes from deuteranopes. For example a two-digit number, say the number 42, will be read by the protanope as 2 and the deuteranope as 4
Ishihara tests were also available as circles, squares and winding lines for use with patients aged 4-6 years or for 'unlettered persons'. The professor's original watercolours were revised by his daughter. As illiterates might not understand a pen (and reflecting the origin of the pictures) the charts were supplied with a soft artist's paintbrush for the patient's use in tracing the curves.
Several editions include a note to the effect that, even when in everyday use, it was recommended that the practitioner keep the book closed to prevent colour fading.
If you can't read what is shown on an old pseudoisochromatic plate it doesn't necessarily mean you are colour blind. The chart may have been produced in a foreign language using unfamiliar characters. They are very adaptable in this way. The picture shows a Far-eastern version from the second quarter of the 20th century contained in a folder bearing oriental script on the front. The donor travelled in the Far East during the Second World War and brought this back with him as a souvenir.
In 1948 a 9th edition, containing 32 coloured plates was issued. The publisher's note is especially interesting evidence for this Post-War date:
In response to the demand for this work from all three branches of the Services, as well as from many medical men engaged in the examination of personnel, it was decided to apply to the Patent Office for the necessary licence to reprint, the work being copyright in all countries signing the Berne Convention. Royalties on copies sold are paid to the Custodian of Enemy Property. They will be dealt with ultimately as may be determined by His Majesty's Government. The Publishers desire to acknowledge the work of the Chiswick Press for their care in producing this facsimile of the original
An American competitor to the Ishihara test, was the H-R-R test, produced in 1955 by American Optical Co and named after its devisers, Dr LeGrand H. Hardy (1895-1954), Dr Gertrude Rand (1886-1970) and M. Catherine Rittler (1905-1987). This was based on research work originally conducted in the Knapp Memorial Laboratory of Physiolgical Optics, the Institute of Ophthalmology of Presbyterian Hospital and the Department of Ophthalmology of the College of Physicians and Surgeons of Columbia University, New York and it was the last completed work of the first-named author. American Optical had produced a set of PIPs for the US military as early as 1940, consisting of 46 plates copied from either Ishihara or Stilling. This entirely new set of plates, in 1955, was intended to be more widely available, at least in its home market.
We have a copy of the second edition, first issued in 1957, which merely altered the order of the plates slightly and continued to be commercially available until about 1970. (It was reissued by another publisher, Richmond International, in the 1990s). The makers claimed it could not only screen for colour vision defects but also give an indication of the degree of defect. Unlike some of the numbers used by Ishihara, the symbols of the H-R-R test were easy to differentiate. If a patient did not know the correct term, he or she could give the symbol their own name, for instance calling an 'O' a ball or a circle. Some British optometrists encouraged the patient to refer to the 'X' as a kiss and the 'O' as a hug. Less affectionately, the Delta symbol was most commonly described as a triangle.
Other Two-dimensional Colour Vision Tests
On the right are Dr W.A. Nagel's Test Cards for Colour Blindness, translated by A. Brewer, opthhalmic surgeon. Each set comprises twelve colour test cards consisting of rings of coloured dots. Willibald Nagel (1870-1911) was director of research in sensory physiology at the Berlin Physiologic Institute from 1902-8 and Professor of Physiology at Rostock from 1908-11.
Learning to distinguish colours is just part of our visual development in childhood. On the left are two stereo vision training cards incorporating colour recognition exercises. They are samples from the Eric Bateman Visual Colour Training Series No 1 produced in the 1960s. This was a set of 33 colour training cards bearing double photographs with only the primary colours showing, mounted on curving stereoscope cards. The cards bear images of bottles, teacups, cubes, balls, plastic ducks and toy cats on skis!
There is also a set of London scenes including Horseguards, The National Gallery, The Tower of London (White Tower), Tower of London (gateway), Piccadilly Circus, the church of St. Martin-in-the-Fields and a red telephone box. It's nice to think that an English optician, designing a test he knew would be supplied across the world, took the trouble to promote the capital's tourist trade at the same time!
Two dividers were also provided to separate the 'Child' cards from the 'Juvenile' cards. Bateman had a specialist interest in vision development and worked for many years alongside a child psychologist.
Do you have memories of being diagnosed with defective colour vision? What tests were used? How did it go on to affect your schooling or your job? Email the museum with your reminiscences.